1. Technical Field of the Invention
This invention relates to telecommunication systems and, more particularly, to a redundant mobile switching center (MSC) architecture for a radio telecommunications network.
2. Description of Related Art
In existing networks which utilize the Global System for Mobile Communications (GSM), each base station system (BSS) or group of BSSs is controlled by one mobile switching center (MSC). This is because GSM networks today are based on circuit switching, so that the networks are configured as trees. One or more base transceiver stations (BTSs) report to a base station controller (BSC), and one or more BSCs, in turn, report to a xe2x80x9cparentxe2x80x9d MSC. Therefore, if an MSC goes down, the entire coverage area served by that MSC and its base stations is xe2x80x9coff the air,xe2x80x9d and no one can make use of that part of the network. Thus, the MSC becomes a single point of failure for the entire service area.
In principle, it is possible to configure a radio telecommunications network as a xe2x80x9cmeshxe2x80x9d network by adding circuits between BSCs and noncontrolling MSCs. However, these circuits are not cost effective to implement since they are dedicated for use only in the failure mode. There has never been a sufficient economic incentive, therefore, to make the modifications required in order to support failover between MSCs.
There are no known prior art teachings of a solution to the aforementioned deficiency and shortcoming such as that disclosed herein. In order to overcome the disadvantage of existing solutions, it would be advantageous to have an architecture for a radio telecommunications network and a method of utilizing the architecture to efficiently provide for MSC redundancy. The present invention provides such a solution.
In one aspect, the present invention is a telecommunications network architecture providing failover operations between mobile switching centers (MSCs). The network architecture includes a communications network such as an Internet Protocol (IP) network in which transmission paths and control paths are logically separated. A plurality of MSCs and at least one base station controller (BSC) are connected to the network. The BSC reports to a primary MSC and includes an alternative MSC list identifying at least one backup MSC for the primary MSC. The BSC also includes means for determining when the primary MSC has failed, means for notifying the backup MSC that the BSC has switched its reporting to the backup MSC, and means for sending mobile station communications to the backup MSC.
In another aspect, the present invention is a method in a telecommunications network of providing failover operations between MSCs. The network includes a plurality of MSCs, at least one BSC reporting to an original (primary) MSC, and at least one home location register (HLR) associated with mobile stations operating in the coverage area of the BSC. The method includes the steps of connecting the MSCs and the BSC to a communications network such as an IP network in which transmission paths and control paths are logically separated, detecting in the BSC that the primary MSC has failed, and identifying at least one backup MSC for the primary MSC. The method also utilizes a control path in the communications network to notify the backup MSC that the BSC has switched its reporting to the backup MSC, and utilizes a transmission path in the communications network to send mobile station communications from the BSC to the backup MSC.
The method may also include the steps of sending a mobile station location updating request from the backup MSC to the HLR, the location updating request including a new element that informs the HLR that the backup MSC is now serving the mobile station due to a failure of the lo primary MSC. This is followed by downloading subscriber information from the HLR to a visitor location register (VLR) in the backup MSC, and sending routing number requests from the HLR to the backup MSC when an incoming call is received in the HLR for a mobile station which has been moved to the backup MSC.
In yet another aspect, the present invention is a method in a telecommunications network of providing failover operations between MSCs in which the network has a plurality of MSCs, at least one BSC reporting to an original (primary) MSC, and at least one HLR associated with mobile stations operating in the coverage area of the BSC. The method includes the steps of connecting the MSCs and the BSC to an IP network in which transmission paths and control paths are logically separated, detecting in the BSC that the primary MSC has failed, identifying at least one backup MSC for the primary MSC, and switching operations to the backup MSC utilizing a control path in the IP network. Then, in each cell affected by primary MSC failure, the BSC broadcasts an indication of when each mobile station is to perform location updating. Thereafter, the BSC sends mobile station communications to the backup MSC utilizing a transmission path in the IP network.